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Old May 30, 2012, 09:30 PM   #1
WWWJD
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What does a good ladder test look like?

I imagine it looks like this. Started playing with the 175gr Matchkings in the .308. Started at 42.6gr and walked up in .2 increments to 43.8 (groups 1-7). Groups 4 and 5 are impressive; 5 has three on top of each other. It was great to see the groups shrink and then start to open up again. Shot these round robin. This also was my first use of the Forster Shoulder Bump Neck Sizing Die.

Groups 10 and 11 are my 168gr loads with some seating depth tweaks; that load didn't get any better in either seating direction off of my previous best. That one is officially done (last week shot a .292moa 5 shot group at 200). Now these 175s are getting my full attention.



Group 9 was shot with Federal Game Shok in the ol' Marlin 60 .22! The old girl still gots it! (my first gun; 22 years old now.) I put a new scope on her last week, and for gits n' shiggles, filled the stock with sand to try and balance it out a bit. Added about 2 lbs, but boy is it solid!. Need to try some CCI in that one; see what happens.
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Last edited by WWWJD; May 30, 2012 at 09:38 PM.
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Old May 31, 2012, 01:42 AM   #2
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Handgun ladders I'll do in .2gr steps. Rifle ladders on most of my cartridges have a pretty wide min and max load, so I'll run one ladder in .5gr steps, and then tune in the .2gr step up or down once I've located the sweet spot.
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Old May 31, 2012, 08:13 AM   #3
WWWJD
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That's what I did last time for the 168. Tightened it up this time around on a hunch that it would be in the same general area of charge weights. One thing that strikes me different this time around: I was seeing more dramatic differences last time around with the 168gr and the .2 increments. These 175s appear to be playing better with the OCW approach. It's a 1:12 twist, so at the moment that seems to make some sense to me.
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Old May 31, 2012, 09:37 AM   #4
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Did you chronograph these shot groups? I would be interested in seeing if groups 4 and 5 had lower ES's.

I have noticed that when I get below .75 MOA (100yrds), it seems to be more of an handloading technique issue that helps tighten my groups.

Have you shot several groups with either #4 or #5 to see if your results are consistant at that charge?

BTW, very good shooting!
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Old May 31, 2012, 09:55 AM   #5
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Sorry in advance for the drift but every time I hear the term ladder test, I think about the one I use as an elevator on my bowling ball cannon.



Here is a video
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Old May 31, 2012, 10:47 AM   #6
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Dangnation jmorris! Is that thing legal? Looks like it would be more of a test of the operator than the ladder.

WWWJD - Are you going to play with the seating depths using the Group 4/5 loads?
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Old May 31, 2012, 10:51 AM   #7
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WWWJD,

Nice example.

It looks to me, using Newberry's criterion, like 2 through 7 all have about the same POI and group size within statistical reason. I know you see smaller groups at 4 and 5, but with 5 shots per group your 95% confidence interval (2 standard deviations) estimated from the average diameter of those six 5-shot groups is 0.177" to 0.415", meaning you'd expect 95% of all 5 shot groups to be within that diameter range. All six of those groups fall safely within that range.

As to the center locations of the groups, going by eyeballing the grid, group three looks like it's centered about a tenth to an eighth of an inch to the right of the average for the rest, and group six looks centered about two tenths of an inch higher than the average for the rest. (Those numbers can be verified by the center of POI from POA data in On Target). But when I plugged in the eyeballed values to find average and standard deviations for the vertical and horizontal POI, the center locations were still well within 2 standard deviations for each axis. The horizontal stayed almost within 1.2 standard deviations, or within 78% of the estimated population of horizontal POI 5-shot group averages, and the .2" high vertical POI shift in target 6 is still within about 1.4 standard deviations or within 84% of expected vertical average for all groups of 5. 5 groups out of 6 is 83% of the total sample of 6 groups, so it's a very reasonable to expected a worst case group center error to be in that ballpark.

So my conclusion is that shots 2 through 7 have apparently got the same group size and POI within expected confidence limits, and also have the same group sizes within 95% confidence limits. In your shoes what I would do next is make up 15 rounds each of 3 loads. One would be load 2, one would be a new load half way between loads 4 and 5 (43.3 grains, if I'm counting correctly), and one would be load 7. Shoot 15 shot groups with each of the three. Do it in round robin style again. That will shrink the uncertainty range by not quite 2/3 of what it is with 5 shot groups.

If you do that, PM me with the results (and a link back to this thread so I don't loose track). Then I can calculate whether you have a statistically significant difference between the three 15 shot groups or not. If there is a significant difference, it may push the center a little more in one direction than the other. If not, you'd just want to stay with that middle load and figure it will serve well and give you some wiggle room for changing conditions.

If all that additional testing is too much trouble to do, you could also just go to that 43.3 grain load now, and be pretty confident it's a good one.
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Old May 31, 2012, 02:11 PM   #8
WWWJD
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Definitely going to shoot these again in higher numbers; UncleNick, I'll play along! It's not too much trouble at all; been hitting the range every Wednesday night after work (it's my hump day quiet time). I'll try these out next week and PM you for sure.

jmorris, you need about a 3" industrial grade dump valve in place of that ball valve.. get your chamber pressures up. ;-)
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Old May 31, 2012, 05:38 PM   #9
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WWWJD, It looks to me that you got it going on, now move on to a different caliber,,, say 7mm rem mag!!(nobody likes you)
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Old June 2, 2012, 05:53 PM   #10
WWWJD
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Hey Unclenick....

... I'm ready to participate in your statistical analysis. 15 each of 42.8, 43.3, 43.8.



I'll shoot you a message Wednesday. Thanks,
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Old June 2, 2012, 08:34 PM   #11
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http://www.duosafety.com/faq.html

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Old June 2, 2012, 08:38 PM   #12
WWWJD
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^^Nice.
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